The present invention is related to the field of syntactic materials, more particularly to methods of manufacturing and supplying syntactic materials and related shipping packages.
Expandable thermoplastic resinous or syntactic materials are typically comprised of combinations of expandable thermoplastics and thermosettable matrix resins. Expandable syntactic materials have properties such as application tailored density and a high compression strength that make them ideal for reinforcing composite and honeycomb structures in aerospace craft. U.S. Pat. No. 2,958,905 to Newberg et al. and U.S. Pat. No. 2,959,508 to Graham et al. describe the use of expandable syntactic materials to form moulded syntactic articles. Generally, a mass of expandable thermoplastic resinous material is placed in a confining mould form or cavity. An exothermically self-reacting agent is added to the thermoplastic resinous material and an external heat source, such as an autoclave or an oven, is used to initiate a reaction involving the agent. The agent""s reaction generates heat and causes expansion of the thermoplastic resinous material to fill the mould form. Despite the weight and strength advantages of the expandable syntactic materials, the formation processes described above are difficult to control so as to achieve a homogenous distribution of the expandable syntactic material.
U.S. Pat. No. 5,783,272 to Wong describes the production of an expandable film that has a relatively uniform density and thickness across its breadth. After manufacture, the film is shipped to a work site and is manipulated into a shape to meet the user""s requirements. The film is then cured so that it expands and fills the mould or cavity.
In one example of the use of such films, the syntactic film (SynSpand(copyright) 9899CF or 9899.1CF from Loctite Corporation of Bay Point, Calif.) is supplied in 1 ft by 2 ft sheets having a thickness of approximately 100 mils. The sheets are cut into a desired shape and used to form a syntactic article, such as a drag link area reinforcement for an aircraft component. The drag link area reinforcement has a three-dimensional shaped body 210 that includes four local reinforcement pads 211 and two tooling-pin locating pads 212, as shown in FIG. 1. As the syntactic film sheets do not match the thickness of the body of the drag link reinforcement, two sheets must be stacked to form the body and additional multiple sheets must stacked to form the pads. Once the basic drag link shape has been formed by cutting and stacking the sheets, the sheets are laid-up onto honeycomb core and/or layered carbon fiber sheets to form an assembly which is then cured to embed the syntactic material. In another example, a hinge pad reinforcement 213 requires three trimmed and stacked sheets of syntactic film, as shown in FIG. 2. Despite the advantage of producing a more homogenous distribution of the syntactic material, on-site construction of the ply kits results in significant waste of the syntactic material and requires a large amount of manual labor and machine kitting resources.
Therefore, it would be advantageous to have a method of deploying expandable syntactic materials on-site without encountering difficult process requirements that lower the quality of the resulting article. It would be further advantageous if the article could be manufactured on-site without a large amount of manual labor or waste of the syntactic materials.
The present invention addresses the above needs and achieves other advantages by providing a method of manufacturing and supplying a net-moulded article of expandable syntactic material and related shipping package. The moulded article is formed at a manufacturing facility where the forming process can be controlled to ensure production of quality syntactic material articles. The moulded article is formed by dispensing the material into a mould having a cavity with a shape matching that of a desired syntactic article to be used in an assembly at a point of use. The mould and moulded article are covered with a protective film to form a mould kit and the mould kit is shipped to the point of use location. At the point of use location, the moulded article is removed from the mould and preferably immediately deployed in the assembly without significant cutting, trimming, forming or other labor intensive actions. Once positioned, the net-moulded article and the assembly are cured to integrate the moulded article with the assembly.
In one embodiment, the present invention includes a method of manufacturing a net-moulded syntactic article at a manufacturing facility and supplying the article to a point of use. The manufacturing and supply method includes supporting an empty mould defining a cavity that has a geometry congruent to a desired or predefined geometry of the net-moulded syntactic article. A syntactic material is placed into the mould until the cavity is filled with the material. As the material fills the cavity, it conforms to the geometry of the cavity. The mould is removed from its support, and the mould with the net-moulded syntactic article therein are packaged for safe transport such that the mould serves as a shipping package. The mould and net-moulded syntactic article are then transported from the manufacturing facility to the point of use. Once at the point of use, the net-moulded syntactic article is removed from the mould and is positioned in an assembly configured to accept the net-moulded syntactic article.
In one aspect, the mould is durable enough to be reusable and can be returned to the manufacturing facility after the net-moulded syntactic article is removed. The returned mould can then be filled again with amorphous syntactic material and transported back to the point of use. Such reusability provides a supply chain management option to the parties wherein the return of the mould, or a quantity of moulds, is a signal that additional net-moulded articles are required at the point of use. Also, the relatively quick xe2x80x9cjust-in-timexe2x80x9d manufacture and deployment of the net-moulded article provide the option of transporting the article and mould at ambient temperature instead of at the freezing temperatures necessary to extend the life of the syntactic material.
In yet another aspect, a film or other cover may be placed over the mould and sealed to the mould so as to protect the net-moulded syntactic article therein during shipping. The film may be at least partially transparent to facilitate viewing of the net moulded syntactic article during shipment. Once at the point of use, the film is removed from the mould and the net-moulded article is removed from the mould cavity and deployed in the assembly.
In another aspect, the mould may be formed on a die which is also used to support the mould while it is being filled with amorphous syntactic material. For instance, the mould may be constructed of a thin sheet material vacuum drawn into a cavity of the die. Once the mould is formed on the die, the amorphous syntactic material can be injected into the cavity of the mould.
The present invention has several advantages. The net-moulded syntactic article is configured at the manufacturing site for immediate deployment into the assembly at the on site location without trimming, stacking or other additional steps. Such trimming and stacking is labor-intensive and typically results in wasted syntactic material. In addition, the material consistency of the syntactic article is improved because process controls are more easily exercised at the manufacturing site than at the point of use. The mould itself serves as a shipping container, cutting down on the number of steps required for packaging and shipping the syntactic article. In addition, return of the mould reduces materials costs and serves to notify the manufacturing location of the need for another net-moulded syntactic article at the point of use. The combination of quick installation of the net-moulded article and the use of a returned mould as a demand signal supports a xe2x80x9cjust-in-timexe2x80x9d manufacturing process. Such short-term manufacturing also allows the syntactic article to be shipped at ambient temperature, obviating the need for frozen storage during shipping and before installation.